Monday, November 24, 2014

We are well into winter in the Northern Hemisphere--Thanksgiving holidays are just around the corner in the US--and for much of the area, this is time defined by cold, dark, and snow. So it seemed appropriate to write a post about snow.

Much of the Northern Hemisphere, the Antarctic, and alpine areas are historically snow covered for more than two months of the year. In parts of the Arctic, snow cover may last 9 months of the year.

From Marchand 2014.

Though only a few degrees different from rain, snow alters an ecosystem through its unique physical properties. It is a physical force, an ecological pressure, and an opportunity: snow alters movement, creates and destroys habitat, and places immense pressures on individuals and species. The ecological implications of snow are immense and wide-ranging.

Snow has unique physical properties that make it particularly important, compared to equivalent amounts of precipitation. It stores energy and water. It insulates the soil underneath it, buffering it from cold temperatures and slowing its eventual re-warming. Snow limits light to the plants underneath it, reducing photosynthesis, and drastically cutting primary productivity during its stay. In addition to these physical properties, the sheer weight of snow has to be considered. Plants beneath a pile of snow risk compression, breakage, and deformation.

A heavy blanket of snow, variable in its depth and consistency, changes the matrix and thus significantly alters movement: snow can ease dispersal, make it much more costly, or even prevent it altogether. Ease of movement in snow is in turn is tied to foraging and predation success. For example, small, lightweight vertebrates such as shrews become active underneath the snow, tunnelling in search of food and constructing nests under deep cover. For them, snow cover may aid winter survival. On top of the snow, some animals (hares, fox, etc.) enjoy ease of movement. If individuals are light enough to travel over the top of the snow, snow can reduce landscape complexity, burying brambles and filling hollows. However, for larger species, snow may come at a cost. Moose or reindeer for example, with their large masses and long, slender legs are at risk when snow depths are too high or a hard crust covers the snow. In these conditions, they may sink, slowing their escape from lighter predators.

Snow is difficult for all life, but plants in particular cannot escape. Places with long winter seasons and late snow melt filter out all but the most adapted vegetation. The plants common to Arctic and alpine areas share many life-history traits. Similar groups of species - mosses, lichens, low-growing shrubs, and grasses - are found in all of these areas. Such species have developed strategies for the conditions, such as seed germination cued by freeze/thaw cycles, small leaf areas to reduce water loss. There are also opportunities. Snow insulates – plants may benefit from burial under drifts, or from collecting snow in dead tissue above ground. Adaptations may permit early growth under thinning snow in the spring, by allowing photosynthesis in cold conditions and low light.

The type, amount and depth of snow-cover may differentiate plant communities on a fine scale, between wind-exposed ridges where drought tolerance is necessary, and snow-accumulating depressions where tolerance of short growing seasons is required. Early naturalist literature recognized these snow-driven micro-differences, describing them as “schneetälchen” or little snow valleys. The Front Range of Colorado has been used for a number of studies of snow gradients on vegetation, and while many environmental factors vary along snow-melt gradients, the timing of snow melt alone greatly affects species presence and abundance.

Diagram of micro-habitats in alpine areas in Colorado, where snow affects vegetation dynamics.

Distribution of 2 species in relation to snow depth. Both from Walker et al (2001)

Snow can be a significant source of water, sometimes the majority of water necessary for the year. It is also a sink for nutrients (N, S) from the atmosphere, the canopy, and the soil – leading it to sometimes be called ‘poor man’s fertilizer’. This isn’t always for the best – high concentrations of N and S in snowmelt can damage plant tissues, and snowdrifts can be reservoirs for airborne pollutants. In samples from the Athabasca River (Alberta, Canada), upstream of oil sands facilities, dissolved polycyclic aromatic compound levels averaged between 0.025-0.03 ug/L. However, measures from melting snow around the river had concentrations up to 4.8 ug/L, suggesting that spring snowmelt could have large environmental impacts.

These nutrients in snow support unique microbial life. Snow algae, bacteria, yeasts and snow fungi arise. Snow algae are adapted to a life history spent wholly within melting snow – these algae find homes in glaciers, alpine peaks, and the dry valley lakes of Antarctica. These species have various adaptations to a snow-bound life, including enzymes resistant to freezing, and special pigments. These unique populations help replace some of the lost winter primary productivity. Small invertebrates graze on snow microbes, and the energy flows into local food webs.

So snow is unique, with wide-ranging implications for ecology and evolution where it occurs. But now snow is changing. Warming temperatures are having widespread and disastrous effects on snow ecosystems around the world. Arctic and alpine systems are among the most vulnerable regions to climate change, and the effects are already showing. Changes in the snow cover, depth and the timing of snowmelt are altering plant phenology and fitness, and restructuring local communities. The effects of changes in snow may be incredibly complex, may interact or be independent from changes in temperatures, and thus are difficult to predict. Some effects of changes in snow (and ice) are already obvious – for example, Glacier National Park in the US is likely to be glacier-less in 30 years. Polar bears, so reliant on their frozen habitat, face a very difficult future. But other effects are very subtle, and may take years to be fully recognized. For example, changes in snow conditions may decrease dispersal and gene flow between Canada lynx (Lynx Canadensis) populations which occur at different ends of a winter climate gradient. With declines in gene flow, the lynx may separate into two increasingly (ecologically?) distinct groups. Shrub encroachment in the low Arctic is a prime example of the complexity of changes in snow. Data shows that shrubs are increasing in abundance in the Arctic over the last 50 years. The snow-shrub hypothesis suggests that this is - indirectly - an outcome of increased snowfall in these regions (though note that warming temperatures are also causing this snow to melt earlier). Shrubs in the region accumulate larger amounts of snow in their branches, resulting in greater insulation and warmer soil temperatures. These warming temperatures encourage greater microbial activity, and perhaps enhance mineralization. The species most able to take advantage of these altered soils are, in fact, more shrubs. All of these examples are reminders that snow - and the organisms adapted to places full of snow - is changing.

Monday, November 17, 2014

*Guest post by Monica Choy -one of several posts selected from the graduate EES3001 Scientific Literacy course at University of Toronto-Scarborough.

Photo
credit: Elodie A. Sampere, Getty Images

Suni, a 34 year old male northern white rhinoceros, died on October 17,
2014 of natural causes. His death reduced the total number of known northern white
rhinos to an alarming six individuals, which has brought his species one step
closer to extinction.1

Suni was born in a zoo in the Czech Republic and was the first of his
kind to be born in captivity. Unfortunately, northern rhinos are a finicky
species when it comes to breeding and with increasing pressures from poaching,
it became critical to provide the animals with a natural, comfortable space.

As a result in 2009, Suni and three others were transported to the Ol
Pejeta Conservancy in East Africa.It was
believed this change in scenery would most accurately imitate their natural
environment.2 Rhino conservationists anticipated that the rhinos
would then breed naturally and provide a healthy calf that would bring new hope
for the waning species.

Even before these desperate attempts to keep the species going however,
the history of the northern rhino has been a sad one. At the time of Suni’s
birth, his species was on a very slow rebound. Northern white rhinos had been excessively
poached for their horns, and their initial population of over 2,000 animals
declined to a shocking 15 rhinos by the late ’80s. Conservation efforts were
ramped up in the ’90s and it looked as though the animals were making a gradual
comeback. Unbelievably, poachers also increased their efforts and knocked the
numbers back down to below 10 individuals by the mid-2000s.3

Northern white rhinos were declared extinct in the wild by 2008.

The likelihood that Suni’s species will become extinct in our lifetime
has increased significantly with his death. And although the Ol Pejeta
Conservancy will continue trying until the bitter end with the use of techniques
such as artificial insemination, the precarious position the northern white
rhino is in, as stated in their press release, is “a sorry testament to the
greed of the human race.” 1

The extinction of such a charismatic species is a tragedy and should
bring awareness to how heavily humans really affect our environments. Although
the northern white rhino may be on the brink of extinction, there are still a
countless number of other species out there that need our help. It is up to us
to work together in order to keep other species as far from the fate of the
northern rhino as possible.

Thursday, November 13, 2014

*Guest post by Jethro Valido -one of several posts selected from the graduate EES3001 Scientific Literacy course at University of Toronto-Scarborough.

Photo from
Adopt-a-Pond at Toronto Zoo

When I think about
turtles, the first things to come to mind are that they are slow and that
they’ve been on Earth for forever. So it came to me as a surprise when I found
out that most of Ontario’s turtles are actually endangered and at risk of
disappearing in Ontario. In fact, seven out of the eight turtle species found in
Ontario are threatened

and
are in dire need of help in order to maintain populations. The problem with
turtles are that they are extremely long-lived (can live up to 70+ years) and
that they have a late sexual maturation (20-25 years). This makes it hard for
us to study them and pin-point a cause to their decline, especially when action
is required immediately.

So what exactly can we
do to help their numbers from declining? One way we can help our turtles is through a head-start program. A head-start
program is the process in which juveniles (in this case turtle eggs) are raised
in captivity until they reach a certain age, and then they are release back
into the wild. This is exactly what I am doing at the Toronto zoo; where we are
head-starting the Blanding’s turtle.

The
Blanding’s Turtle is one of the threatened species of turtles in Ontario. It
can be easily identified and differentiated from other native turtles by its
yellow throat and jaw. The biggest threats to this species are associated with
humans; ranging from habitat loss due to land development, to being hit by cars
when trying to cross roads due to habitat fragmentation, to predation from urban
wildlife, such as raccoons, coyotes, skunks, etc. Though once numerous, their
numbers have drastically declined, and to help restore their numbers, we are
implementing a head-start program for this species at the zoo. This will help
encourage the young to grow to maturity, where they have a higher success rate
at surviving than when juveniles.

Photo from Adopt-a-Pond at Toronto Zoo

The head-start program
starts off with looking for Blanding’s turtle nests in at-risk locations. These
locations are areas such as crop fields, where the eggs they would not have a
good chance for survival. These eggs are then transported to the Toronto zoo
where they are raised in captivity until they are 2 years old. The reason for
this is to prevent predation. At birth, the turtles are very small and are easy
prey for animals such as raccoons. By raising them until they are 2 in what
could be called a “safe haven” for the turtles, they can grow to a sufficient size
to deter predation once released. By deterring predation, their chances for
survival is increased. Once released,
the turtles are tracked by radio-tracking devices and monitored.

The
really interesting part about this all as a research student working at the
Toronto zoo, is that there a lot of questions around the idea and process of
head-starting. Although head-starting has been successful for sea turtles, its
success is unknown for these freshwater turtles we have in Ontario; including
Blanding’s turtle. The Toronto zoo is invested in this project long term,
especially since the Blanding’s turtle has a late maturation, thus this project
will be heavily research-based to understand the effects head-starting has on
these turtles and whether the protocols are well-suited for the turtles.
Because of this, there is a huge range of flexibility in adjusting or improving
protocols and it is really something that can be applied to other turtle
species around the world.

Photo from Adopt-a-Pond at Toronto Zoo

The Adopt-a-Pond Program
at the Toronto zoo is heavily involved with this project and they are quite
determined to restore our Blanding’s turtle populations. With the release of
these two year old turtles, Adopt-a-Pond is as well restoring their habitat;
wetlands. Not only will these turtles receive help but they will act as an
umbrella species to protect other threatened wetland species as well. Though we
are not 100% certain whether head-starting will restore the Blanding’s turtle
populations, this project is just a step in aiding declining turtle
populations. From this, hopefully we can gain and discover answers to many of
the questions concerning its decline, and eventually manage a long-term
solution. Though
rare today, hopefully one day, I can walk around the Rouge Park and bump into a
yellow-throated turtle.

Here
are some additional links:

-Adopt-a-Pond Blog http://adoptapond.wordpress.com/ - Here, you can follow the Adopt-a-Pond team on their blog.
They post up plenty of blogs following the status of their turtles (including
Blanding’s turtles) and their releases

-Earth Rangers Bloghttp://www.earthrangers.org/blog/ - Here, you can follow
the Earth Rangers blog (Earth Rangers are in partnership to head-start the
Blanding’s turtle). The website is mostly for children but they have posted up
head-starting blogs.